The mRNA 3'-end processing reaction has been shown to play an important role in modulating Ig heavy chain poly(A) site use in B-cell development. This proposal focuses on defining the mechanisms of action of hnRNPF and H/H', auxiliary polyadenylation factors, and how they operate to influence poly(A) site choice during the induction of myeloma/plasma and lymphoma/memory B cells. We propose the following: Aim 1. To define the role of hnRNP F in binding RNA and blocking 3' end processing in cells. A. We will test the hypothesis that specific domains of hnRNP F are responsible for its RNA binding and inhibition of 3' end processing. B. We will test the hypothesis that the differences between hnRNP F and the closely related proteins hnRNP H/H', in the carboxyl-terminal region and between RNA binding domains 2 and 3, are responsible for the differing biological effects of these molecules on 3' processing. C. We will test the hypothesis that specific phosphorylation of CTD will enhance the competition between hnRNP F and CstF-64. AIM 2. We will test the hypothesis that differential loading of 3'-end processing factors occurs both along the Ig heavy chain gene and during different stages of B-cell development. AIM 3. We will test the hypothesis that over-expression of hnRNP F in authentic plasma cells will suppressIg heavy chain secretion by reducing the amount of secretory specific mRNA. AIM 4. We hypothesize that the increased expression of PC4 we have seen in plasma cells influences 3'-endformation by interacting directly with CstF-64.The experiments described in this proposal attempt to find differences in cells that may serve as markers to identify memory, naive, and plasma B-cells as well as to understand the molecular events that determine how memory an/or B-cells may be activated to differentiate into plasma cells. Understanding plasma cell development is important for vaccine development to eradicate infectious diseases, mediating allergic responses and autoimmune diseases, and limiting tumor growth. Understanding the control of polyadenylation is important for understanding and possibly controlling aspects of cell growth, differentiation and malignancy.